Resource Use of Arctic Peregrine Falcons along the Colville River, Alaska (RWO 90 Annual Report, 2013)

Abstract

To improve knowledge about the ecology, life history, and behavior of arctic peregrine falcons (Falco peregrinus tundrius) on the Colville River Special Area (CRSA), we proposed to (1) summarize and evaluate existing CRSA arctic peregrine nesting data to assess trends in territory occupancy and abundance, (2) assist in summary and evaluation of existing data on nesting habitat use and related productivity, (3) implement additional data collection and analysis efforts to address information needs, and (4) use results of the first three objectives to address management implications in the CRSA. To address the first objective in 2013, we used a long‐term dataset developed from breeding arctic peregrine surveys to evaluate how occupancy dynamics of individual nest sites and entire nesting cliffs were related to abiotic and biotic factors. We developed competing dynamic occupancy models with hypotheses for the probabilities of initial occupancy, colonization, local extinction, and detection, and used a stepwise procedure and information‐theoretic techniques to select the best‐approximating models. Initial occupancy probability was positively correlated with the amount of surrounding prey habitat and height of the nest site above the Colville River. Colonization probability was also positively correlated with nest height, and negatively correlated with the date of snow melt and distance to the nearest nest site occupied by a conspecific, the latter of which is likely a consequence of variability in resources along the river. Local extinction probability varied with aspect and was negatively correlated with productivity from the previous year (i.e., site quality), amount of prey habitat, and height. Colonization and local extinction probabilities were positively and negatively correlated, respectively, with threshold and logarithmic functions of year. Detection probabilities varied across years and were lower during second surveys. Our results demonstrated relationships between multiple abiotic and biotic factors and arctic peregrine falcon occupancy dynamics, and suggested certain nest sites and cliffs in the CRSA could be protected differently than others. Nest sites and cliffs with historically higher productivity were occupied most frequently and had a lower probability of local extinction between years. This suggests protection measures around higher quality nest sites and cliffs would have the most impact on breeding peregrine population dynamics, and offers the possibility that current regulations in the CRSA Management Plan could be relaxed around infrequently occupied nest sites. Also related to our first objective, we used the long‐term dataset to conduct an initial analysis to assess factors related to abundance and population dynamics of arctic peregrines on cliffs. In 2014 and in relation to our third objective, we will complete analyses and develop a model of arctic peregrine resource selection, and use results to produce a map documenting historical and predicted probability of use throughout the CRSA. The results of our analyses will help identify the abiotic and biotic factors having the most influence on arctic peregrines nesting along the Colville River, and evaluate critical information needs.